1. Field of the Invention
The present invention relates to fluid management flow devices such as a catheter device and methods useful with such devices, and in particular hydrocephalus shunts containing an antibiotic and/or drug to minimize the risk of blockage or obstruction inside of the catheter while improving protection against colonization of gram-positive bacteria and/or tissue proliferation when the devices are combined with uniform fluid flow enhancing tips.
2. Related Art
Hydrocephalus is a neurological condition that is caused by the abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles, or cavities, of the brain. CSF is a clear, colorless fluid that is primarily produced by the choroid plexus and surrounds the brain and spinal cord. CSF constantly circulates through the ventricular system of the brain and is ultimately absorbed into the bloodstream. CSF aids in the protection of the brain and spinal cord. Because CSF keeps the brain and spinal cord buoyant, it acts as a protective cushion or “shock absorber” to prevent injuries to the central nervous system.
Hydrocephalus, which affects children and adults, arises when the normal drainage of CSF in the brain is blocked in some way. Such blockage can be caused by a number of factors, including, for example, genetic predisposition, intraventricular or intracranial hemorrhage, infections such as meningitis, head trauma, or the like. Blockage of the flow of CSF consequently creates an imbalance between the amount of CSF produced by the choroid plexus and the rate at which CSF is absorbed into the bloodstream, thereby increasing pressure on the brain, which causes the ventricles to enlarge.
Some of these problems can be treated by backflushing, which is a process that uses the CSF present in the shunt system to remove the obstructing matter. This process can be ineffective, however, due to the small size of the pores of the ventricular catheter and due to the small amount of flushing liquid available in the shunt system. Other shunt systems have been designed to include a mechanism for flushing the shunt system. For example, some shunt systems include a pumping device within the system which causes fluid in the system to flow with considerable pressure and velocity, thereby flushing the system. As with the process of backflushing, using a built-in mechanism to flush the shunt system can also fail to remove the obstruction due to factors such as the size of the pores and the degree and extent to which the pores have been clogged.
Occluded ventricular catheters can also be repaired by cauterizing the catheter to remove blocking tissue, thereby reopening existing pores that have become occluded. Alternatively, new pores can be created in the catheter. These repairs, however, may be incapable of removing obstructions from the ventricular catheter depending on the location of the clogged pores. Additionally, the extent of tissue growth into and around the catheter can also preclude the creation of additional pores, for example, in situations where the tissue growth covers a substantial portion of the ventricular catheter. Another disadvantage of creating new apertures to repair an occluded ventricular catheter is that this method fails to prevent or reduce the risk of repeated obstructions.
Because attempts at flushing or repairing a blocked ventricular catheter are often futile and ineffective, occlusion is more often treated by replacing the catheter. Although this can be accomplished by simply removing the obstructed catheter from the ventricle, the growth of the choroid plexus and other tissues around the catheter and into the pores can hinder removal and replacement of the catheter. Care must be exercised to avoid damage to the choroid plexus, which can cause severe injury to the patient, such as, for example, hemorrhaging. Not only do these procedures pose a significant risk of injury to the patient, they can also be very costly, especially when shunt obstruction is a recurring problem
U.S. Pat. No. 4,917,686, the disclosure of which is hereby incorporated by reference, describes implanted medical devices (such catheters, valves, molded parts, etc. and including hydrocephalus shunts and central venous catheters) that have been treated with antimicrobial agents to combat the problem of colonization of bacteria particularly on the interior surfaces of the device.
US 2003/0216710, the disclosure of which is whereby incorporated by reference, describes a catheter having one or more inlet holes along the length of the catheter whereby the cross-sectional areas of successive inlet holes decreases, the decrease first occurring at the inlet hole immediately following the most proximal inlet hole. Such a design purports to alter the typical inflow of fluid into the catheter such that a disproportionately high volume of fluid no longer enters the most proximal inlet hole. The decrease in inflow at the most proximal inlet results in less deposition of debris within the catheter at this position.
Lin et al., in “Computational and Experimental Study of Proximal Flow in Ventricular Catheters”, (J. Neurosurgery 99:426-431, 2003), the disclosure of which is hereby incorporated by reference, describes and demonstrates that drainage hole geometry is indeed a factor in achieving uniform flow patterns within ventricular catheters. FIG. 2 of Lin dramatically demonstrates the flow distribution improvement when catheter hole geometry is modified. The problem addressed by Lin relates to obstructing agents such as blood clots, cell clusters and normal tissue as causing occlusion of the catheter at its proximal end. There is no mention of antimicrobial or drug based implantable medical devices such as catheters or shunts in an attempt to alleviate occlusion of the catheter lumen caused by biofilm formation through bacterial colonization or occlusion by tissue proliferation.
Accordingly, there exists a need for fluid management flow implants, such as shunts and catheter shunt systems that minimize or eliminate the risk of blockage or obstruction in the implant and reduces the possibility of bacterial biofilm or tissue occlusion within the lumens and inner surfaces of the implants.